- From: <noah_mendelsohn@us.ibm.com>
- Date: Wed, 16 Jan 2002 18:54:51 -0500
- To: Walter.Waterfeld@softwareag.com
- Cc: "'xmlschema-dev@w3.org'" <xmlschema-dev@w3.org>
Dr. Walter Waterfeld asks: >> is it possible to extend the lexical space of >> simple datatype, without changing its value space? As Jeni has responded the answer is no. If we allowed you to do this, how would we make sure that processors around the world understood your extensions? Schemas is, to a significant degree, designed to foster a high level of interoperability across organizations that may not have had prior contact with each other (e.g. to promote business to business electronic commerce.) Extensions of the sort you propose seem unlikely to be understood without software upgrades. In general, we have avoided features with that characteristic. BTW: for similar reasons, we have avoided the very great temptation to allow extensible validation rules. I'm sure mathemeticians would find a "prime number" type to be very useful, but we don't allow you to include in the schema the logic to ensure "primeness" in an interoperable way. You can easily establish a standard name for such types, and build specialized processors to do the additional validation if you like. Given that you want extensions rather than restrictions (primes are a restriction of integers), that would be harder to do in an interoperable way, unless you arbitrarily defined your new date type as an extension of string. I hope this explains some of the reasons for the current design. Thank you. ------------------------------------------------------------------ Noah Mendelsohn Voice: 1-617-693-4036 IBM Corporation Fax: 1-617-693-8676 One Rogers Street Cambridge, MA 02142 ------------------------------------------------------------------
Received on Wednesday, 16 January 2002 19:07:57 UTC